Genome-wide linkage scan for plasma high density lipoprotein cholesterol, apolipoprotein A-1 and triglyceride variation among American Indian populations: the Strong Heart Family Study

Deep Learning for Inference of Hepatic Proton Density Fat Fraction From T1-Weighted In-Phase and Opposed-Phase MRI: Retrospective Analysis of Population-Based Trial Data

BACKGROUND. The confounder-corrected chemical shift-encoded MRI (CSE-MRI) sequence used to determine proton density fat fraction (PDFF) for hepatic fat quantification is not widely available. As an alternative, hepatic fat can be assessed by a two-point Dixon method to calculate signal fat fraction (FF) from conventional T1-weighted in- and opposed-phase (IOP) images, although signal FF is prone to biases, leading to inaccurate quantification. OBJECTIVE. The purpose of this study was to compare hepatic fat quantification by use of PDFF inferred from conventional T1-weighted IOP images and deep-learning convolutional neural networks (CNNs) with quantification by use of two-point Dixon signal FF with CSE-MRI PDFF as the reference standard. METHODS. This study entailed retrospective analysis of data from 292 participants (203 women, 89 men; mean age, 53.7 ± 12.0 [SD] years) enrolled at two sites from September 1, 2017, to December 18, 2019, in the Strong Heart Family Study (a prospective population-based study of American Indian communities). Participants underwent liver MRI (site A, 3 T; site B, 1.5 T) including T1-weighted IOP MRI and CSE-MRI (used to reconstruct CSE PDFF and CSE R2* maps). With CSE PDFF as reference, a CNN was trained in a random sample of 218 (75%) participants to infer voxel-by-voxel PDFF maps from T1-weighted IOP images; testing was performed in the other 74 (25%) participants. Parametric values from the entire liver were automatically extracted. Per-participant median CNN-inferred PDFF and median two-point Dixon signal FF were compared with reference median CSE-MRI PDFF by means of linear regression analysis, intraclass correlation coefficient (ICC), and Bland-Altman analysis. The code is publicly available at github.com/kang927/CNN-inference-of-PDFF-from-T1w-IOP-MR. RESULTS. In the 74 test-set participants, reference CSE PDFF ranged from 1% to 32% (mean, 11.3% ± 8.3% [SD]); reference CSE R2* ranged from 31 to 457 seconds-1 (mean, 62.4 ± 67.3 seconds-1 [SD]). Agreement metrics with reference to CSE PDFF for CNN-inferred PDFF were ICC = 0.99, bias = -0.19%, 95% limits of agreement (LoA) = (-2.80%, 2.71%) and for two-point Dixon signal FF were ICC = 0.93, bias = -1.11%, LoA = (-7.54%, 5.33%). CONCLUSION. Agreement with reference CSE PDFF was better for CNN-inferred PDFF from conventional T1-weighted IOP images than for two-point Dixon signal FF. Further investigation is needed in individuals with moderate-to-severe iron overload. CLINICAL IMPACT. Measurement of CNN-inferred PDFF from widely available T1-weighted IOP images may facilitate adoption of hepatic PDFF as a quantitative bio-marker for liver fat assessment, expanding opportunities to screen for hepatic steatosis and nonalcoholic fatty liver disease.

Contribution of genetic, biochemical and environmental factors on insulin resistance and obesity in Mexican young adults

Overweight/obesity, dyslipidemias, hypertension and hyperglycemia are strongly related to non-communicable diseases (NCD) in which genetic and environmental factors interact with each other. The Mexican population exhibit a genetic disposition to metabolic syndrome, type 2 diabetes, as well as many forms of dyslipidemia. This study aimed to determine the association between biochemical, genetic and environmental factors in the development of metabolic syndrome (MS), obesity and insulin resistance (IR) in Mexican young adults. Young women and men (n=6750 between 19.3±2.3 years old) participated in a health promotion program from the Autonomous University of Querétaro, México (SU-Salud program). A sub-sample of 665 participants was taken for the determination of single nucleotide polymorphisms (SNP) rs964184 (APOAV), rs9282541 (ABCA1) and rs1260326 (GCKR), using QuantStudio 12K Flex Real-Time PCR System. For the multivariate analysis, a multiple logistic regression was performed. A prevalence of 22% of overweight and 7% of obesity was determined. The main metabolic risk factors were low levels of HDL-C (30%), IR (19%), and a high level of triglycerides (15%). The main factors associated with IR were body fat percentage and triglycerides; SNP for the ABCA1 gene was related to MS, obesity and low HDL-C; SNP for GCKR gene was related to high fasting glycemia, while APOAV SNP was related with MS, hypertriglyceridemia and low HDL-C. Our findings show that the Mexican genetic predisposition to NCD affects young adults, who can suffer MS, obesity and IR. Public health strategies must focus on prevention actions from an early age.

Direct and indirect genetic effects on triglycerides through omics and correlated phenotypes

Even though there has been great success in identifying lipid-associated single-nucleotide polymorphisms (SNPs), the mechanisms through which the SNPs act on each trait are poorly understood. The emergence of large, complex biological data sets in well-characterized cohort studies offers an opportunity to investigate the genetic effects on trait variability as a way of informing the causal genes and biochemical pathways that are involved in lipoprotein metabolism. However, methods for simultaneously analyzing multiple omics, environmental exposures, and longitudinally measured, correlated phenotypes are lacking. The purpose of our study was to demonstrate the utility of the structural equation modeling (SEM) approach to inform our understanding of the pathways by which genetic variants lead to disease risk. With the SEM method, we examine multiple pathways directly and indirectly through previously identified triglyceride (TG)-associated SNPs, methylation, and high-density lipoprotein (HDL), including sex, age, and smoking behavior, while adding in biologically plausible direct and indirect pathways. We observed significant SNP effects (P < 0.05 and directionally consistent) on TGs at visit 4 (TG4) for five loci, including rs645040 (DOCK7), rs964184 (ZPR1/ZNF259), rs4765127 (ZNF664), rs1121980 (FTO), and rs10401969 (SUGP1). Across these loci, we identify three with strong evidence of an indirect genetic effect on TG4 through HDL, one with evidence of pleiotropic effect on HDL and TG4, and one variant that acts on TG4 indirectly through a nearby methylation site. Such information can be used to prioritize candidate genes in regions of interest, inform mechanisms of action of methylation effects, and highlight possible genes with pleiotropic effects.

Linkage and association analysis of obesity traits reveals novel loci and interactions with dietary n-3 fatty acids in an Alaska Native (Yup'ik) population

OBJECTIVE

To identify novel genetic markers of obesity-related traits and to identify gene-diet interactions with n-3 polyunsaturated fatty acid (n-3 PUFA) intake in Yup'ik people.

MATERIAL AND METHODS

We measured body composition, plasma adipokines and ghrelin in 982 participants enrolled in the Center for Alaska Native Health Research (CANHR) Study. We conducted a genome-wide SNP linkage scan and targeted association analysis, fitting additional models to investigate putative gene-diet interactions. Finally, we performed bioinformatic analysis to uncover likely candidate genes within the identified linkage peaks.

RESULTS

We observed evidence of linkage for all obesity-related traits, replicating previous results and identifying novel regions of interest for adiponectin (10q26.13-2) and thigh circumference (8q21.11-13). Bioinformatic analysis revealed DOCK1, PTPRE (10q26.13-2) and FABP4 (8q21.11-13) as putative candidate genes in the newly identified regions. Targeted SNP analysis under the linkage peaks identified associations between three SNPs and obesity-related traits: rs1007750 on chromosome 8 and thigh circumference (P=0.0005), rs878953 on chromosome 5 and thigh skinfold (P=0.0004), and rs1596854 on chromosome 11 for waist circumference (P=0.0003). Finally, we showed that n-3 PUFA modified the association between obesity related traits and two additional variants (rs2048417 on chromosome 3 for adiponectin, P for interaction=0.0006 and rs730414 on chromosome 11 for percentage body fat, P for interaction=0.0004).

CONCLUSIONS

This study presents evidence of novel genomic regions and gene-diet interactions that may contribute to the pathophysiology of obesity-related traits among Yup'ik people.

Phosphodiesterase 3A rs7134375 single nucleotide polymorphism and serum lipid levels

The association between the phosphodiesterase 3A (PDE3A) rs7134375 single nucleotide polymorphism (SNP) and serum lipid levels are not well understood in the general population. The present study was performed in order to detect the association between the rs7134375 SNP and serum lipid levels in the Guangxi Mulao and Han populations. The genotypes of the PDE3A rs7134375 SNP in 761 subjects of the Mulao population and 774 subjects of the Han Chinese population were determined by polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing. It was observed that serum low-density lipoprotein cholesterol and apolipoprotein B levels were higher in the Mulao population than in the Han population (P<0.05 for each). The frequencies of the C and A alleles were 72.14 and 27.86% in the Mulao population, and 78.55 and 21.45% in the Han population (P<0.01), respectively. The frequencies of the CC, CA and AA genotypes were 52.04, 40.21 and 7.75% in the Mulao population, and 61.50, 34.11 and 4.39% in the Han population (P<0.01), respectively. The frequencies of the C and A alleles were 74.89 and 25.11% in Mulao females, and 68.08 and 31.92% in Mulao males (P<0.01), respectively. The serum triglyceride (TG) levels were different among the genotypes in the Mulao population; however, not in the Han population (P<0.01), and the A allele carriers exhibited lower TG levels than the A allele noncarriers. The serum lipid parameters were also correlated with several environmental factors in the two ethnic groups (P<0.05-0.001). It was concluded that the genotypic and allelic frequencies of the rs7134375 SNP are different between the Mulao and Han populations. In addition, the PDE3A rs7134375 SNP is associated with serum TG levels in the Mulao population, however, not in the Han population.

Association of the rs7395662 SNP in the MADD-FOLH1 and several environmental factors with serum lipid levels in the Mulao and Han populations

BACKGROUND

The rs7395662 single nucleotide polymorphism (SNP) in the MADD-FOLH1 has been associated with serum lipid traits, but the results are inconsistent in different populations. The present study was undertaken to investigate the association of rs7395662 SNP and several environmental factors with serum lipid levels in the Guangxi Mulao and Han populations.

METHOD

A total of 721 subjects of Mulao and 727 subjects of Han Chinese were randomly selected from our previous stratified randomized samples. Genotyping of the SNP was performed by polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and confirmed by direct sequencing.

RESULTS

Serum apolipoprotein (Apo) B levels were higher in Mulao than in Han (P < 0.01). The allelic and genotypic frequencies in Han were different between males and females (P < 0.05 for each), but there was no difference between Mulao and Han or between Mulao males and females. The levels of low-density lipoprotein cholesterol (LDL-C) and ApoB in Mulao females were different among the genotypes (P < 0.05), the G allele carriers had higher LDL-C and ApoB levels than the G allele non-carriers. The levels of total cholesterol (TC), triglyceride (TG), LDL-C and ApoB in Han males and TC, TG and high-density lipoprotein cholesterol (HDL-C) in Han females were different among the genotypes (P < 0.05-0.01), the subjects with GG genotype in Han males had higher TC, TG, and ApoB and lower LDL-C levels than the subjects with AA or AG genotype, and the G allele carriers in Han females had lower TC and HDL-C levels than the G allele non-carriers. The levels of LDL-C and ApoB in Mulao females were correlated with the genotypes (P < 0.05 for each). The levels of HDL-C and ApoAI in Han males and HDL-C in Han females were correlated with genotypes (P < 0.05-0.001). Serum lipid parameters were also correlated with several environmental factors in both ethnic groups (P < 0.05-0.01).

CONCLUSION

The association of rs7395662 SNP and serum lipid levels is different between the Mulao and Han populations, and between males and females in both ethnic groups.

Sex-specific association of rs16996148 SNP in the NCAN/CILP2/PBX4 and serum lipid levels in the Mulao and Han populations

BACKGROUND

The association of rs16996148 single nucleotide polymorphism (SNP) in NCAN/CILP2/PBX4 and serum lipid levels is inconsistent. Furthermore, little is known about the association of rs16996148 SNP and serum lipid levels in the Chinese population. We therefore aimed to detect the association of rs16996148 SNP and several environmental factors with serum lipid levels in the Guangxi Mulao and Han populations.

METHOD

A total of 712 subjects of Mulao nationality and 736 participants of Han nationality were randomly selected from our stratified randomized cluster samples. Genotyping of the rs16996148 SNP was performed by polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing.

RESULTS

The levels of apolipoprotein (Apo) B were higher in Mulao than in Han (P < 0.001). The frequencies of G and T alleles were 87.2% and 12.8% in Mulao, and 89.9% and 10.1% in Han (P <0.05); respectively. The frequencies of GG, GT and TT genotypes were 76.0%, 22.5% and 1.5% in Mulao, and 81.2%, 17.4% and 1.4% in Han (P <0.05); respectively. There were no significant differences in the genotypic and allelic frequencies between males and females in both ethnic groups. The levels of HDL-C, ApoAI, and the ratio of ApoAI to ApoB in Mulao were different between the GG and GT/TT genotypes in males but not in females (P < 0.01 for all), the subjects with GT/TT genotypes had higher serum levels of HDL-C, ApoAI, and the ratio of ApoAI to ApoB than the subjects with GG genotype. The levels of TC, TG, LDL-C, ApoAI, and ApoB in Han were different between the GG and GT/TT genotypes in males but not in females (P < 0.05-0.001), the T allele carriers had higher serum levels of TC, TG, LDL-C, ApoAI, and ApoB than the T allele noncarriers. The levels of HDL-C, ApoAI, and the ratio of ApoAI to ApoB in Mulao were correlated with the genotypes in males (P < 0.05-0.01) but not in females. The levels of TC, TG, HDL-C, LDL-C, ApoAI and ApoB in Han were associated with the genotypes in males (P < 0.05-0.001) but not in females. Serum lipid parameters were also correlated with several enviromental factors in both ethnic groups (P < 0.05-0.001).

CONCLUSIONS

The genotypic and allelic frequencies of rs16996148 SNP and the associations of the SNP and serum lipid levels are different in the Mulao and Han populations. Sex (male)-specific association of rs16996148 SNP in the NCAN/CILP2/PBX4 and serum lipid levels is also observed in the both ethnic groups.

Glucuronic acid epimerase is associated with plasma triglyceride and high-density lipoprotein cholesterol levels in Turks

We narrowed chromosome 15q21-23 linkage to plasma high-density lipoprotein cholesterol (HDL-C) levels in Turkish families by fine mapping, then focused on glucuronic acid epimerase (GLCE), a heparan sulfate proteoglycan (HSPG) biosynthesis enzyme. HSPGs participate in lipid metabolism along with apolipoprotein (apo) E. Of 31 SNPs in the GLCE locus, nine analyzed by haplotype were associated with HDL-C and triglyceride levels (permuted p = 0.006 and 0.013, respectively) in families. Of five tagging GLCE SNPs in two cohorts of unrelated subjects, three (rs16952868, rs11631403, and rs3865014) were associated with triglyceride and HDL-C levels in males (nonpermuted p < 0.05). The association was stronger in APOE 2/3 subjects (apoE2 has reduced binding to HSPGs) and reached multiple-testing significance (p < 0.05) in both males and females (n= 2612). Similar results were obtained in the second cohort (n= 1164). Interestingly, at the GLCE locus, bounded by recombination hotspots, Turks had a minor allele frequency of SNPs resembling Chinese more than European ancestry; adjoining regions resembled the European pattern. Studies of glce(+/-) apoe(-/-) mice fed a chow or high-fat diet supported a role for GLCE in lipid metabolism. Thus, SNPs in GLCE are associated with triglyceride and HDL-C levels in Turks, and mouse studies support a role for glce in lipid metabolism.

Genetic loci for blood lipid levels identified by linkage and association analyses in Caribbean Hispanics

To identify genetic loci influencing blood lipid levels in Caribbean Hispanics, we first conducted a genome-wide linkage scan in 1,211 subjects from 100 Dominican families on five lipid quantitative traits: total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), triglycerides (TG), and LDL-C/HDL-C ratio. We then investigated the association between blood lipid levels and 21,361 single nucleotide polymorphisms (SNP) under the 1-logarithm of odds (LOD) unit down regions of linkage peaks in an independent community-based subcohort (N = 814, 42% Dominican) from the Northern Manhattan Study (NOMAS). We found significant linkage evidence for LDL-C/HDL-C on 7p12 (multipoint LOD = 3.91) and for TC on 16q23 (LOD = 3.35). In addition, we identified suggestive linkage evidence of LOD > 2.0 on 15q23 for TG, 16q23 for LDL-C, 19q12 for TC and LDL-C, and 20p12 for LDL-C. In the association analysis of the linkage peaks, we found that seven SNPs near FLJ45974 were associated with LDL-C/HDL-C with a nominal P < 3.5 × 10(-5), in addition to associations (P < 0.0001) for other lipid traits with SNPs in or near CDH13, SUMF2, TLE3, FAH, ARNT2, TSHZ3, ZNF343, RPL7AL2, and TMC3. Further studies are warranted to perform in-depth investigations of functional genetic variants in these regions.